I have been working with expansion chambers for a year, following the designs posted in the Bicimotor Bogota Facebook page.These Exhaust System work properly, especially in the 66cc Two stroke Engine,which is usually sold as 80cc.But in the 48cc engine, they do not work at 100%. My trials in my 48cc engine show a lot of mistakes in the calculation of the expansion chamber, although I have reached the 62 Kph limit on it. According to the EC Calculations, my expansion chamber is a disaster. There is no sinchrony between sizes of diffuser, baffle and belly pieces, besides the header length is out of the recommended, but it works. However, I would like compare it with a 100% effective expansion chamber developed and built for someone in this forum.I apologize for my rookie use of the language.....Thanks to all of you.